Change Windows 8 / Server 2012 Product Key To Complete the Activation

Go to the Start screen then right click at the bottom to get all apps, select “command” and right click. Make sure you choose run as “Administrator” from the bottom options.

In the command prompt, in the given path;

to change the key:

C:\Windows\System32> slmgr.vbs /ipk ABCDE-FGHIJ-KLMNO-PQRST-UVWXY

to activate the key:

C:\Windows\System32> slmgr.vbs -ato

Finally you will get the confirmation – Product Activated successfully.

One more option: